1. Field of the Invention
This invention relates to medical devices and in particular a multi-pole electrode catheter and method for endocardial mapping and ablation. A single catheter is capable both of mapping the atrial and ventricular heart chambers, as well as ablating foci or bypass tracts that cause dysrhythmias.
This is a continuation-in-part of U.S. patent application Ser. No. 06/931,696, filed Nov. 14, 1986.
2. Description of the Prior Art
In the treatment of cardiac dysrhythmias, non-surgical procedures such as management with drugs are favored. However, some dysrhythmias of the heart are not treatable with drugs. In addition, some patients of advanced age or illness may not tolerate invasive surgery to excise tachycardias which cause dysrhythmias.
Endocardial mapping is a technique that typically involves percutaneously introducing an electrode catheter into the patient. The electrode catheter is passed through a blood vessel, the aorta and and thence into an endocardial site such as the atrium or ventricle of the heart. A tachycardia is induced and a continuous, simultaneous recording made with a multichannel recorder while the electrode catheter is moved to different endocardial positions. When a tachardial foci is located as indicated in an electrocardiogram recording, it is marked by means of a fluoroscopic image.
Under earlier techniques, the mapping catheter would be withdrawn and replaced by an ablation catheter. The ablation catheter contained one or more electrodes for delivering a controlled burst of energy, of the order of 100 joules or so, to the foci. The foci would be ablated and the patient monitored for a period of time to ensure that there would be no reoccurence of the dysrhythmia. This removal of the mapping catheter was both time consuming as well as subject to inherent inaccuracies. This is because the location of the tachardial foci could not always be precisely relocated by using the fluoroscope.
As a result, catheters have been developed for the location and ablation of such tachycardias that perform both the mapping and ablation functions with the same catheter. One such mapping and ablation catheter is a hexipolar catheter made by the United States Catheter and Instrument Corporation. This prior art device has a series of six electrode rings in alternating 2 and 5 mm distances along an elongated woven Dacron surface. Bipolar electrograms are used to determine the site for ablation.
Problems with this and other prior art devices are manifest. First, the area of mapping is fairly large and imprecise. That is, the foci can only be found within about 10-12 cm2 and at best only about 2-3 cm of the site.
Corollary to this is that the area ablated must be unduly large since the site of the foci is only known to this precision. The prior art electrode catheters also deliver the ablative charge over a wider than necessary area. This causes tissue and cell damage beyond the foci.
The invention is directed to an endocardial electrode catheter and method for performing both mapping and ablation functions in the same device. The catheter is in the form of a hollow tube having a plurality of side electrodes equally spaced around the distal end thereof. A further, central electrode is fixed to the distal end on the catheter axis. A like plurality of conductor wires pass through the hollow tube and are connected to leads which may be attached to a multichannel EKG machine for taking bipolar and unipolar electrograms. In an alternate embodiment, the wires pass through longitudinal bores within the tube wall.
A cable is contained within the tube and is fixed at its distal end to the central electrode. It is also connected to a lead which is, in turn, connected to the EKG machine. The cable passes through and is affixed to a hollow, elongated rod. The rod, in turn, passes through an end cap of a main body. An actuator knob on the proximal end of the rod allows the cable to be selectively retracted.
A plurality of slits intermediate the side electrodes allows the central electrode to be retracted vis-a-vis the side electrodes as the limbs intermediate and defined by the slits expand radially outwardly. The four side electrodes lie in the same plane and equally spaced from adjacent electrodes. The side electrodes are at the apexes of a square pattern with the central electrode in the center of the square.
A conduit leading to a chamber formed within the main body allows medicament to be conducted through the tube and out through the slits to the endocardial site of the distal end of the catheter.
To accomplish the method of mapping, the leads are connected to a multi-channel EKG machine. The distal end of the catheter is introduced into an endocardial site and recordings are made. The catheter is moved to different endocardial sites until a discontinuity shows on the EKG reading. Before each move, the side electrodes are returned to their fully retracted mode. They are moved to their fully expanded mode when a new site is reached.
To accomplish ablation, the method further provides that electrical energy is then discharged through some or all of the leads and out of the respective electrodes. The electrical, radio frequency, or laser energy ablates the tachycardial foci which was found through mapping. If necessary, further ablation can be accomplished.